Teleconverters, either 1.4X or 2X, are efficient tools to add focal length to the photographer's arsenal. However, universal-type teleconverters have certain limitations in performance when used with ultra-telephoto lenses of 200mm or longer as compensation of chromatic aberration alone becomes highly critical in this focal length range. The new PRO-series teleconverters are specifically designed and optimized for use with such ultra-telephoto lenses to deliver maximum resolution, contrast and color rendition without degrading any aspect of the master lens performance.
The 1.4X teleconverter will increase the focal length of the master lens by 1.4X and make the lens one f-stop slower. The 2X doubles the focal length of the master lens and makes the lens two f-stops slower. In addition to increasing focal length, both teleconverters allow greater magnification in macro since the Minimum Object Distance (MOD) of the master lens does not change when used with the teleconverters.
The 1.4X teleconverter can be used with both AF and MF lenses. AF will be retained if the master lens is F/4.5 or faster. AF will be retained with the 2X teleconverter if the master lens is F/4.0 or faster.
The Tamron 2x is commonly used for Wildlife photos and more.The Tamron 2x is popular because customers like the following qualities of the Tamron 2x: Easily interchangeable and Lightweight
Construction: 4 Groups/ 4 Elements
Dimensions (Length x Diameter): 1.0in. (26mm) x 2.6in. (66.7mm)
Notes: All AF tele-converters and AF extension tubes for Canon EOS are also compatible with Canon EOS "IX" camera for APS system.